join with restrictive clause

[stroy]

3 tables...

Languages
IdLang
Description

Expresssion
IdExp
Date
…

LangExpression
IdExp
IdLand
Description

I need a list of all languages with an indicator (true/false or count…)to know if the expression exist for that language for a specific expression

Language
Fr French
En English
Sp Spanish

Expression
1 10/10/10
2 10/10/10
3 10/10/10

LangExpression
1 Fr jour
1 En day
1 Sp dias
2 Fr nuit
2 En night
3 Fr rue
3 En street

I need for expression 2
FR true
EN true
SP false

If I go with joins, the “WHERE idExp = 2“ removes the SP entry from the resultset.
I use Oracle 8i.
Please help
Thanks

 

[stroy]

I have a solution but I am sure there must be a better way:

select a.idLANG, decode((select b.idLANG from langExpression b, langue c where b.idExp = '2' and c.idLANG = b.idLANG and b.idLANG = a.idlang), null, 'false', 'true') as ok
from langue a

Thanks
Stroy

 

[stroy]

I think I got it right...

select t2.idLANG, decode((select t1.idLANG from langExpression t1 where t1.idexp = '1' and t1.idLANG = t2.idlang), null, 'false', 'true')
from langue t2

thanks